I have a 2002 Taurus wagon with the Duratec engine. The car has 181,000 miles on it.(Yes, we drive that much!!) A year ago I replaced the engine, and while I was at it I replaced the transmission seal. This is where my trouble began.

I managed to put too much transmission fluid in it and apparently blew the transmission seal, so it leaks. I also put Mercon III transmission fluid in it, and this seems to have been a mistake, thought I cannot seem to get a clear consensus on this. I have since started putting the correct Mercon V fluid in it, though now I find that it's a bad idea to mix the two. HOWEVER, I have also recently found transmission fluid that is compatible in both Mercon III and Mercon V transmissions, so I'm really confused!

Frankly, I wish I could just put good ol' Type F in it and forget about it.

Here are my problems: The engine runs a bit rough, coughing like a carburetored car would if the carb needed work. It also has a bit of hesitation when I punch it. Worse, the car seems to be losing power, as in it has been gradually becoming more and more gutless. I don't think the transmission is slipping, as it settles in at about 2100 rpm at around 60 - 65 mph, about where it has been all the years we've owned it.(We bought it new.)

We recently had a code reader hooked up to it, and the codes indicated low voltage at the EGR sensor/solenoid and low flow in the EGR valve (I don't remember the codes, just the symptoms.)

Any ideas? Am I in the process of toasting my transmission? Why is the car so gutless?